forward declaration of class using templates

Question

Can I use forward declaration for template class?
I try:

template<class que_type>
class que;
int main(){
    que<int> mydeque;
    return 0;
}
template<class que_type>
class que {};

I get:

error: aggregate 'que<int> mydeque' has incomplete type and cannot be defined.

Answer 1

This is not a template issue. You cannot use a type as a by-value variable unless it has been fully defined.

Answer 2

No. At the point of instantiation, the complete definition of the class template must be seen by the compiler. And its true for non-template class as well.